1. Field of the Invention
The present disclosure relates to a semiconductor device and a manufacturing method therefor.
2. Description of the Related Art
With higher function and higher performance of electronic devices in recent years, there have been made various studies for achieving higher performance and higher integration of semiconductor devices used in electronic devices. Among these semiconductor devices, a three-dimensional stacked semiconductor device that includes a plurality of stacked semiconductor chips receives attention. In the three-dimensional stacked semiconductor device, it is important to electrically connect two or more stacked semiconductor chips.
As a new technique for bonding a plurality of semiconductor chips, as illustrated in FIG. 5, a direct bonding technique for directly bonding two stacked semiconductor chips 310, 320 together is under consideration (for example, refer to U.S. Patent Publication No. 2005/0161795). First semiconductor chip 31 includes first substrate body 311 which includes a plurality of transistors 312 formed on the principal surface, first wiring layer 313 which covers transistors 312, and first connection layer 314 which includes a plug. First seal ring 302a which includes the plug is disposed from first wiring layer 313 through first connection layer 314. Similarly, second semiconductor chip 320 includes second substrate body 321 which includes a plurality of transistors 322 formed on the principal surface, second wiring layer 323 which covers transistors 322, and second connection layer 324 which includes a plug. Second seal ring 302b which includes the plug is disposed from second wiring layer 323 through second connection layer 324.
As a method for directly bonding two semiconductor chips 310, 320 together, several methods are under consideration. These methods are, for example, a method of cleaning joint surfaces 301 between semiconductor chips 310, 320 to form dangling bonds and covalently bonding the formed dangling bonds to each other, a method of forming a metallic bond of the same kind of metals, and a method of providing amino groups (NHx) or hydroxyl groups (OH) on joint surfaces 301 to form a hydrogen bond or the like. In the direct bonding, it is possible to obtain a covalent bond after bonding by dehydration using a heat treatment at a lower temperature than a temperature in melt-bonding through a bump.
Semiconductor chips can be directly bonded together at room temperature. Thus, it is possible to further reduce a pitch between electrodes than in melt-bonding, which contributes to miniaturization of semiconductor chips. This technique is called direct bonding or room temperature bonding. In the present specification, this technique is called direct bonding. The “direct bonding” described in the present specification means that a metallic bond is formed between metals, or that a covalent bond is formed between insulating films.
As illustrated in FIG. 5, there is generally employed in semiconductor chips 310, 320 a structure in which seal ring 302 surrounds a circuit portion in order to prevent a crack from propagating to the circuit portion, which is generated during dicing for cutting a wafer having the circuit portion into individual chips. Seal ring 302 is formed by directly bonding first seal ring 302a and second seal ring 302b each of which penetrates each circuit part from a lower part through an upper part and is made of a metal. Seal ring 302 also has a role of preventing water from infiltrating into the circuit portion from side surfaces of chips after dicing.
In particular, in a three-dimensional stacked semiconductor device that is made by direct bonding, there is proposed a structure that includes a seal ring continuously formed to connect two silicon substrates by directly bonding metal seal rings formed on the respective silicon substrates at junction interfaces (for example, refer to Unexamined Japanese Patent Publication No. 2012-204443, in particular, FIGS. 9, 10 and 11).